The present disclosure relates to an electronic device package and a method for fabricating the same, and more particularly, to an electronic device package and a method for fabricating the same, capable of preventing contamination and securely bonding an electronic device to the package substrate.
A photosensor is a semiconductor device that is capable of sensing light and providing an electrical output. Image sensors capture the image of an object or scene using an array of photosensors. The market for image sensors is rapidly growing as they are embedded in mobile phones as well as in a digital cameras and camcorders.
In general, the photosensor is an integrated circuit which includes one pixel or an array of pixels for sensing light in its central part, and terminals for transmitting electrical signals of the light sensed by the pixel(s) or other control inputs and outputs or power in its peripheral part. The photosensor may use a chip on board (COB) scheme where the photosensor is directly built into a camera module as a bare chip, or a chip scale package (CSP) scheme where a photosensor chip and a transparent substrate such as a glass substrate are combined and packaged, and then the CSP is built into the camera module. Recently, the CSP is commonly used since it can miniaturize a photosensor package.
Particles, moisture and so on must be prevented from entering the photosensor package, as particles entering into the photosensor package may attach to the pixel region of the photosensor and cause defects in the images. Furthermore, moisture flowing into the photosensor package can degrade the micro-lens or the color filter formed in the photosensor chip. Therefore, the pixel region of the photosensor package should be sufficiently sealed to prevent particles or moisture from entering the pixel region after the packaging.
Today a common method of protecting the pixel region is to use a sealing ring formed of a resin such as epoxy to surround the pixel region. However, the sealing ring formed using the resin cannot seal the pixel region sufficiently since moisture will diffuse through the resin into the pixel region. Moreover, when the photosensor chip is combined with the transparent substrate, a high pressure is generated in the pixel region during subsequent solder reflow processes due to this diffused moisture and thus there may be damage to the resin sealing ring when it is blown out by the high pressure in the pixel region.
To solve the above problem of the resin sealing ring, a solder material such as SnAg is used, and the sealing ring is formed to include an air vent through which the air is released when the solder material is bonded. Furthermore, this sealing ring has a spiral structure where one end surrounds the other end to include an air vent. However, since moisture in some cases may flow into the pixel region through the air vent in case of the sealing ring including the air vent, it is impossible to perfectly block the inflow of moisture. The vented sealing ring structure assures that the pressure inside the pixel area and outside the sealing ring are always at the same pressure, thus assuring that the sealing ring is never damaged during subsequent reflow processes.
Meanwhile, it is possible to form the sealing ring in a closed loop shape with SnAg solder having a low melting point. As this sealing ring is typically formed on top of a polymer layer on the photosensor, some moisture can still penetrate under the sealing ring and enter the pixel area. Thus during subsequent processing, such as SMT (Surface Mount Technology) reflow, the SnAg is in a liquid state and there may be a blowout phenomenon in a part of SnAg sealing ring due to the increase in pressure in the pixel area cavity.